Project Abstract The muscular dystrophies (MDs) are a heterogeneous group of inherited muscular disorders characterized by muscle wasting and weakness, and they affect both children and adults. The worldwide prevalence of inherited neuromuscular diseases estimated in a review study was 28.6/100,000, and 33.3/100,000 if rarer disorders were included. As a group, these disorders cover a considerable proportion of patients with chronic disease, while recent studies of prevalence of the MDs in the United States are lacking. For this project, we propose utilizing the experience acquired and methods developed over the past 16 years to improve on an already established muscular dystrophy surveillance system conducting longitudinal, population-based surveillance and research of eligible MDs by identifying individuals with eligible MDs, and conducting longitudinal follow-up and research. We plan to continue our multiple source surveillance efforts, as they have been effective for the Muscular Dystrophy Surveillance, Tracking and Research Network (MD STARnet). Further, our proposed use of administrative data will lower costs while enhancing case identification to yield more complete prevalence rates. Second, we will capitalize on the extensive network of expertise our site has developed throughout the years to develop a survey that complements the surveillance data and helps address the critical analytic questions posed by the organizations and patient advocacy groups which represent individuals affected by the various muscular dystrophies. Lastly, ensuring that patients with rare diseases get access to the best quality diagnosis and care presents challenges that are best addressed through collaborations and sharing of resources. By working with stakeholders such as patient organizations, clinicians, and researchers, and sharing our findings with policy makers and payers, our efforts may be used to improve systems of care to provide maximal results at minimal costs, including the financial costs to society and the burden of care for families. We will be partnering with local, state and national programs and patient advocacy groups during project development and sharing study findings often. Successful collaboration and wide distribution of study findings will improve the lives of patients and their families, and may lead to additional clinical studies in order to enhance knowledge about rare diseases.